How to Fix 'systemctl service failed' Error in Linux: Complete Troubleshooting Guide

The Problem: Service Won't Start

You try to start a service and get this:

$ sudo systemctl start myapp
Job for myapp.service failed because the control process exited with error code.
See "systemctl status myapp.service" and "journalctl -xe" for details.

Or variations like:

• Failed to start <service>.service
• Service has no installation config
• Unit <service>.service could not be found

Stop. Don't panic. Don't reinstall. This guide will fix it.

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Understanding Systemd Services

Before fixing, understand what systemd is:

• Modern init system for Linux (replaced SysVinit)
• Manages all services/daemons (nginx, mysql, your app)
• Uses "unit files" (.service files) for configuration

When a service fails, systemd captures why it failed. Your job is to read those logs correctly.

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Error #1: Service Failed to Start (Generic)

Symptom

$ sudo systemctl start nginx
Job for nginx.service failed. See 'systemctl status nginx' and 'journalctl -xe' for details.

Step 1: Check Service Status

sudo systemctl status nginx

Example Output:

● nginx.service - A high performance web server
   Loaded: loaded (/lib/systemd/system/nginx.service; enabled)
   Active: failed (Result: exit-code) since Mon 2025-03-10 10:00:00 UTC; 5s ago
  Process: 12345 ExecStart=/usr/sbin/nginx -g daemon off; (code=exited, status=1/FAILURE)
 Main PID: 12345 (code=exited, status=1/FAILURE)

Mar 10 10:00:00 server nginx[12345]: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Mar 10 10:00:00 server nginx[12345]: nginx: [emerg] still could not bind()
Mar 10 10:00:00 server systemd[1]: nginx.service: Failed with result 'exit-code'.

Key Information:

• Active: failed - Service is not running
• exit-code - The process exited with an error
• Error Message: bind() to 0.0.0.0:80 failed (98: Address already in use)

Root Cause: Port 80 already in use by another process.

Step 2: Check Detailed Logs

sudo journalctl -u nginx -n 50 --no-pager

Flags explained:

• -u nginx = Show logs for nginx unit
• -n 50 = Last 50 lines
• --no-pager = Print all at once (no scrolling)

Step 3: Fix the Root Cause

For "port already in use":

# Find what's using port 80
sudo ss -lntp | grep :80

Output:

LISTEN  0  128  0.0.0.0:80  0.0.0.0:*  users:(("apache2",pid=8888,fd=4))

Solution: Apache is using port 80. Stop it:

sudo systemctl stop apache2
sudo systemctl disable apache2  # Prevent auto-start on boot
sudo systemctl start nginx

Step 4: Verify

sudo systemctl status nginx
# Should show: Active: active (running)

curl localhost:80
# Should return HTML

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Error #2: Configuration File Syntax Error

Symptom

$ sudo systemctl restart nginx
Job for nginx.service failed. See 'systemctl status nginx' and 'journalctl -xe' for details.

Step 1: Status Check

sudo systemctl status nginx

Output shows:

nginx: [emerg] unexpected "}" in /etc/nginx/nginx.conf:45
nginx: configuration file /etc/nginx/nginx.conf test failed

Root Cause: Syntax error in config file.

Step 2: Test Configuration

Most services have a test command:

# Nginx
sudo nginx -t

# Apache
sudo apache2ctl configtest

# HAProxy
sudo haproxy -c -f /etc/haproxy/haproxy.cfg

Output:

nginx: [emerg] unexpected "}" in /etc/nginx/nginx.conf:45
nginx: configuration file /etc/nginx/nginx.conf test failed

Step 3: Fix Config

Open the file and fix line 45:

sudo nano /etc/nginx/nginx.conf
# Go to line 45, fix the syntax error

Common mistakes:

• Missing semicolon ;
• Extra closing brace }
• Typo in directive name

Step 4: Test Again

sudo nginx -t
# nginx: configuration file /etc/nginx/nginx.conf test successful

sudo systemctl restart nginx

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Error #3: Permission Denied

Symptom

$ sudo systemctl start myapp
Job for myapp.service failed. See 'systemctl status myapp' and 'journalctl -xe' for details.

Logs show:

Mar 10 10:00:00 server myapp[1234]: /usr/bin/python3: can't open file '/opt/myapp/app.py': [Errno 13] Permission denied

Step 1: Check File Permissions

ls -lah /opt/myapp/app.py

Output:

-rw------- 1 root root 1234 Mar 10 09:00 /opt/myapp/app.py

Problem: File is owned by root, but service runs as myapp user (as defined in unit file).

Step 2: Check Service User

sudo systemctl cat myapp | grep User

Output:

User=myapp

Service runs as myapp user but file is owned by root.

Step 3: Fix Ownership

sudo chown -R myapp:myapp /opt/myapp

Step 4: Fix Permissions

# Directories: 755 (rwxr-xr-x)
sudo find /opt/myapp -type d -exec chmod 755 {} \;

# Files: 644 (rw-r--r--)
sudo find /opt/myapp -type f -exec chmod 644 {} \;

# Make main script executable
sudo chmod +x /opt/myapp/app.py

Step 5: Restart

sudo systemctl restart myapp
sudo systemctl status myapp
# Active: active (running)

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Error #4: Missing Dependencies

Symptom

Service starts then immediately crashes.

sudo systemctl status myapp

Output:

Active: failed (Result: exit-code)
Process: 1234 ExecStart=/usr/bin/node server.js (code=exited, status=1/FAILURE)

Logs show:

Error: Cannot find module 'express'

Step 1: Check Application Logs

sudo journalctl -u myapp -n 50

Step 2: Fix Missing Dependencies

# For Node.js
cd /opt/myapp
sudo -u myapp npm install

# For Python
cd /opt/myapp
sudo -u myapp pip3 install -r requirements.txt

Important: Run as the service user (myapp), not as root.

Step 3: Restart

sudo systemctl restart myapp

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Error #5: Service Unit Not Found

Symptom

$ sudo systemctl start myapp
Failed to start myapp.service: Unit myapp.service not found.

Step 1: Verify Unit File Exists

ls -l /etc/systemd/system/myapp.service
# or
ls -l /lib/systemd/system/myapp.service

If file doesn't exist, you need to create it.

Step 2: Create Unit File

sudo nano /etc/systemd/system/myapp.service

Example Template:

[Unit]
Description=My Application
After=network.target

[Service]
Type=simple
User=myapp
WorkingDirectory=/opt/myapp
ExecStart=/usr/bin/node server.js
Restart=always
RestartSec=10
StandardOutput=journal
StandardError=journal
SyslogIdentifier=myapp

[Install]
WantedBy=multi-user.target

Step 3: Reload Systemd

Critical Step: Systemd needs to re-scan for new unit files.

sudo systemctl daemon-reload

Step 4: Enable and Start

sudo systemctl enable myapp  # Start on boot
sudo systemctl start myapp

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Error #6: Dependency Failed

Symptom

$ sudo systemctl start myapp
Job for myapp.service failed because a dependency job failed.

Step 1: Check Dependencies

systemctl list-dependencies myapp

Output:

myapp.service
● ├─postgresql.service  ← Failed!
● ├─network.target

Step 2: Fix Dependency

# Start the failed dependency
sudo systemctl start postgresql

# Then start your service
sudo systemctl start myapp

Step 3: Modify Unit File (If Needed)

If PostgreSQL should auto-start before your app:

sudo nano /etc/systemd/system/myapp.service

Add:

[Unit]
After=postgresql.service
Requires=postgresql.service

Reload and restart:

sudo systemctl daemon-reload
sudo systemctl restart myapp

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Using journalctl Like a Pro

Follow Logs Real-Time

sudo journalctl -u myapp -f

This is your debugging window. Keep it open while you restart the service in another terminal.

Filter by Time

# Last hour
sudo journalctl -u nginx --since "1 hour ago"

# Specific time range
sudo journalctl -u myapp --since "2025-03-10 10:00" --until "2025-03-10 11:00"

# Today's logs
sudo journalctl -u myapp --since today

Show Only Errors

sudo journalctl -u myapp -p err

Priority levels:

• emerg (0) - System is unusable
• alert (1) - Action must be taken immediately
• crit (2) - Critical conditions
• err (3) - Error conditions
• warning (4) - Warning conditions
• notice (5) - Normal but significant
• info (6) - Informational
• debug (7) - Debug-level messages

Disk Space Management

Logs can grow huge. Clean old logs:

# Keep only last 7 days
sudo journalctl --vacuum-time=7d

# Keep max 500MB
sudo journalctl --vacuum-size=500M

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Common Mistakes Users Make

1. Not Running daemon-reload

After editing .service file, always:

sudo systemctl daemon-reload

Without this, systemd won't see your changes.

2. Using service Instead of systemctl

Old command:

sudo service nginx start  # Deprecated!

Modern way:

sudo systemctl start nginx

3. Not Checking Logs

Don't just run start and hope. Always check:

sudo systemctl status myapp
sudo journalctl -u myapp -n 50

4. Running as Root Unnecessarily

Bad:

[Service]
User=root  # Security risk!

Good:

[Service]
User=myapp  # Run as dedicated user

5. Forgetting to Enable

Service starts now but won't survive reboot:

sudo systemctl start myapp  # Start now
sudo systemctl enable myapp  # Start on boot

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Prevention: Best Practices

1. Always Test Config Before Reload

# Test first
sudo nginx -t

# Only reload if test passes
sudo systemctl reload nginx

2. Use Restart Policies

In your .service file:

[Service]
Restart=on-failure
RestartSec=10

This auto-restarts on crashes (but not on manual stop).

3. Set Resource Limits

Prevent runaway processes:

[Service]
MemoryMax=512M
CPUQuota=50%

4. Monitor Services

Install monitoring (Prometheus, Netdata, or simple cron):

# Simple healthcheck script
#!/bin/bash
if ! systemctl is-active --quiet myapp; then
    echo "Service myapp is down!" | mail -s "Alert" admin@example.com
    sudo systemctl restart myapp
fi

5. Backup Unit Files

Before editing:

sudo cp /etc/systemd/system/myapp.service /etc/systemd/system/myapp.service.backup

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Troubleshooting Workflow Checklist

When a service fails, follow this order:

• [ ] Run sudo systemctl status <service>
• [ ] Read the error message carefully
• [ ] Run sudo journalctl -u <service> -n 50
• [ ] Identify root cause (port, config, permissions, dependency)
• [ ] Fix the root cause
• [ ] Test configuration if applicable (nginx -t, etc.)
• [ ] Run sudo systemctl daemon-reload if unit file changed
• [ ] Run sudo systemctl restart <service>
• [ ] Verify with sudo systemctl status <service>
• [ ] Test functionality (curl, browser, etc.)

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Emergency Recovery

Service Won't Stop

# Force stop
sudo systemctl kill -s SIGKILL myapp

# Then clean restart
sudo systemctl restart myapp

Systemd Itself is Broken

# Re-execute systemd
sudo systemctl daemon-reexec

Last Resort: Boot to Single User Mode

If system won't boot due to service failure, at GRUB:

1. Press e to edit boot parameters
2. Add systemd.unit=rescue.target to kernel line
3. Press Ctrl+X to boot into rescue mode
4. Fix the broken service
5. Disable it: systemctl disable broken-service
6. Reboot

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Conclusion

95% of "service failed" errors come down to:

1. Port conflicts - Use ss -lntp
2. Config errors - Use nginx -t or equivalent
3. Permission issues - Check chown and chmod
4. Missing dependencies - Install them
5. Forgot daemon-reload - Run it after changes

Master these, and you'll troubleshoot like a senior sysadmin.

Pro Tip: Keep sudo journalctl -u <service> -f running in a separate terminal whenever you're debugging services. Real-time logs are invaluable.